The control of every movement, whether it is a basic reflex or a sophisticated skill, is highly complex, involving the control of muscles distributed throughout the limb and body. This complexity is present whether movements are produced naturally by the nervous system or artificially by rehabilitation engineers for the restoration of movement following motor impairments. Understanding the neural strategies used to overcome these complexities can therefore potentially provide new advances in our ability to restore movement following injury. We take this approach in the proposed research, attempting to translate insights derived from basic experimental and theoretical research in order to improve strategies used to restore motor function. The experiments performed in this research are based on two recently proposed principles for the simplification of biological motor control. The first principle suggests that the nervous system uses muscle synergies to reduce the number of variables that need to be specified in the production of movements. In this hypothesis, each such 'synergy'controls the activation of a small group of muscles, with complex movements produced by flexibly combining multiple synergies. The second principle suggests that the nervous system exploits the intrinsic dynamics of the limb in order to increase the efficiency of motor control. In this hypothesis, the properties of the muscles and skeleton allow certain motor commands to be particularly effective in producing movements. In this proposal, we combine these two principles in order to develop a novel strategy for the restoration of motor function following injury. In particular, we will develop and evaluate a controller based on muscles synergies which are designed to exploit the intrinsic dynamics of the limb. We have shown in simulation work that this hypothesis is capable of producing a wide range of movement efficiently and effectively. The proposed experiments will extend this simulation work and evaluate this strategy directly by using it to reanimate a paralyzed limb. Specifically, this research will 1) use experimental measurements of the musculoskeletal dynamics to identify a low dimensional representation of the rat hindlimb, 2) identify a set of muscle synergies which controls the intrinsic dynamics of the rat hindlimb, 3) then finally use these synergies to produce movements in a paralyzed limb. This research will therefore directly test whether this strategy of using muscle synergies to exploit intrinsic limb dynamics is capable of restoring motor function following injury. This work will take recent novel theoretical research and translate it to an experimental situation with direct clinical relevance. The results of this research therefore have the potential to significantly advance clinical applications using control strategies to restore movement in patients with motor impairments. PUBLIC HEALTH RELEVANCE: The research in this proposal will evaluate a novel strategy for restoring motor function following paralysis. This strategy will greatly simplify the control of limb movements using functional electrical stimulation, increasing the efficiency and efficacy of rehabilitation strategies. The experiments to be performed in this research therefore have the potential to significantly advance clinical applications for the restoration of function in patients with motor impairments.